Chapter 3 Synthetic Fibres and Plastics mcqs & important questions science | class 8th

MCQ Questions for Class 8 Science: Ch 3 Synthetic Fibres and Plastics

1. Polythene and PVC are examples of

(a) Bio degradable substance

(b) Thermosetting plastics

(c) Thermoplastics

(d) Rayon

► (c) Thermoplastics

2. _____ is blended with wool for making carpets.

(a) Rayon

(b) Nylon

(c) Polystyrene

(d) Polyester

► (a) Rayon

3. Fabric is made of

(a) steel

(b) fibre

(c) paper

(d) none of these

► (b) fibre

4. The raw materials used in making nylon

(a) Wood pulp

(b) Cellulose

(c) Coal, water, air

(d) All of these

► (c) Coal, water, air

5. Which of the following set of features belong to thermoplastics ?

(a) soft and brittle

(b) hard and strong

(c) hard and less brittle

(d) soft and less brittle

► (d) soft and less brittle

6. Which of the following is a thermosetting plastic ?

(a) Nylon

(b) PTFE

(c) Polyester

(d) Melamine

► (d) Melamine

7. First synthetic fibre formed from natural material is:

(a) Rayon

(b) Acrylon

(c) Nylon

(d) Polyester

► (a) Rayon

8. Statement incorrect for synthetic fibres is/are:

(a) non-biodegradable

(b) very expensive

(c) long lasting

(d) all the above

► (b) very expensive

9. The first man-made fibre is

(a) nylon

(b) polyester

(c) rayon

(d) cotton

► (c) rayon

10. Why is it not advisable to wear clothes made up of synthetic fibres in hot and humid weather?

(a) Synthetic fibres catch fire very easily.

(b) Synthetic fibres do not absorb sweat.

(c) Synthetic fibres stick to the body.

(d) Both (b) and (c).

► (d) Both (b) and (c).

11. A man- made fibre obtained from natural source is :

(a) Acrylic

(b) Nylon

(c) Rayon

(d) Polyester

► (c) Rayon

12. Fibre obtained by chemical treatment of wood pulp is called ___________.    

(a) Natural silk

(b) Rayon

(c) Nylon

(d) Polyester

► (b) Rayon

13. When plastics are burnt they release:

(a) oxygen gas

(b) biogas

(c) toxic gases

(d) nitrogen gas

► (c) toxic gases

14. The strongest fibre is called:

(a) rayon

(b) nylon

(c) acrylic

(d) none of these

► (b) nylon

15. Remoulding can be done of :

(a) Polyvinyl chloride

(b) Bakelite

(c) Melamine

(d) Formaldehyde

► (a) Polyvinyl chloride

16. Raw materials for the synthetic fibres are derived from :

(a) petroleum products

(b) plant products

(c) animal products

(d) only coal

► (a) petroleum products

17. The lightweight plastic material is :

(a) Polypropylene

(b) Polythene

(c) Bakelite

(d) Polyester

► (a) Polypropylene

18. The small units used in making synthetic fibres are:

(a) molecules

(b) polymers

(c) cells

(d) none of these

► (b) polymers

19. Which of the following is not a characteristic of plastics?

(a) Plastics are poor conductors of heat.

(b) Plastics are insoluble in water.

(c) Plastics are non-inflammable.

(d) Plastics do not react with water and air.

► (c) Plastics are non-inflammable.

20. The oldest synthetic plastic is :

(a) Polyester

(b) Bakelite

(c) Melamine

(d) Polythene

► (b) Bakelite

21. Plastics are generally made from

(a) coal

(b) plant products

(c) kerosene

(d) petroleum

► (d) petroleum

22. Which of the following is used for making stockings and parachutes?

(a) Bakelite

(b) Wool

(c) Nylon

(d) Cotton

► (c) Nylon

23. Which of the following materials is the best for making garments and jackets that can be used in wet or damp environment?

(a) Polyester

(b) Wool

(c) Cotton

(d) None of these

► (a) Polyester

24. The fibre made up by the chemical treatment of wood pulp is

(a) Rayon

(b) Nylon

(c) Polyester

(d) None of these

► (a) Rayon

Synthetic Fibres and Plastics Class 8 Extra Questions Short Answer Questions

Question 1.
What are polymers?
Answer:
Polymers are compounds that are made up of same, small repeating units, joined together through bonds in a linear pattern.

Question 2.
What is cellulose?
Answer:
Cellulose is a polymer made up of large number of glucose units.

Question 3.
List the two ways in which synthetic fibres can be synthesised.
Answer:
Synthetic fibres may be synthesised by two ways:

• By regenerating them from natural fibres, like in rayon.
• By using entirely chemicals and chemical reactions, like in nylon.

Question 4.
What is rayon?
Answer:
Rayon is a man-made fibre which is produced by the chemical processing of wood pulp, i.e., a natural substance.

Question 5.
List two uses of rayon.
Answer:
The two uses of rayon are:

• It is used to make apparels like shirts, blouses, etc.
• It is used to make furnishings and upholstery.

Question 6.
List any two properties of rayon.
Answer:
The two properties of rayon are:

• Rayon is a versatile fibre.
• It can be dyed in different colours.

Question 7.
Draw a diagram to show the:
(a) linear arrangement of units in plastic.
(b) cross-linked arrangement of units in plastic.
Answer:

Question 8.
Write some advantages of synthetic fibres.
Answer:
Advantages of synthetic fibres are:

• Synthetic fibres are strong and durable.
• They do not shrink.
• They are moth and insect resistant.

Question 9.
What are plastics?
Answer:
Plastics are those substances which are mostly synthetic in nature, obtained mainly from petrochemi¬cal sources and can be moulded into different shapes.

Question 10.
What is plasticity?
Answer:
Plasticity is the property of materials by which they can be moulded into any shape.

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Question 11.
What are thermosetting plastics?
Answer:
Thermosetting plastics are those which when moulded once, cannot be softened again and lose their plasticity.

Question 12.
List any three properties of plastics.
Answer:
The three properties of plastics are:

• They are non-corrosive in nature.
• They are light in weight and durable.
• They do not conduct heat.

Question 13.
What are the uses of polyester?
Answer:
The uses of polyester are:

• It is used in making home furnishings and apparels.
• Polyester is used for finishing on guitars and pianos.

Question 14.
Why is it advised not to wear synthetic clothes while working in a laboratory or working with fire in the kitchen?
Answer:
The synthetic fibres melt on heating. This is actually a disadvantage with synthetic fibres. If the cloth catches fire it can be very disastrous. The fabric melts and sticks to the body of the person wearing it. It is therefore advised not to wear synthetic clothes while working in a laboratory or working with fire in the kitchen.

Question 15.
Write some properties and uses of melamine.
Answer:
Melamine is a versatile material. It resists fire and can tolerate heat better than other plastics. It is used for making floor tiles, kitchenware and fabrics which resist fire.

Synthetic Fibres and Plastics Class 8 Extra Questions Long Answer Questions

Question 1.
Describe about nylon. Write its uses and properties.
Answer:
Nylon is the strongest amongst all the synthetic fibres. It is fully synthetic polymer which is prepared from coal, water and air. It is a polymer of amides. It was made in 1931 for the first time. It was used as a supplement of silk when silk got deficient during World War II for many military applications. Uses of Nylon

• Nylon is used in toothbrushes, combs, etc.
• It is used to make parachutes, tents, ropes, etc.
• It is used to make socks and stockings as it is elastic.
• It is widely used for making clothes, carpets, etc.

Properties of Nylon

• It melts on heating.
• It absorbs less water.
• It is resistant to moths and fungi.
• It has high tensile strength.
• It is durable.

Question 2.
Write the advantages of synthetic fibres.
Answer:
Synthetic fibres has many advantages as compared to natural fibres. Some of them are as follows:

• They are very strong and durable.
• They are cheaper in cost as compared to natural fibres.
• They absorb less water and are quick to dry.
• They do not shrink.
• They are very useful for saving our trees and animals as they are made up of chemicals.
• They are moth and insect resistant.

Question 3.
List the common varieties of polyester. Also mention the natural fibres which are used for blending to enhance their properties.
Answer:
Polyester could be blended with natural fibres to enhance its properties. The common varieties of polyester are:

• PET (Polyethylene terephthalate)
• Terrycot: It is made by blending polyester and cotton.
• Terrysilk: It is made by blending polyester iaiid silk.
• Terrywool: It is made by blending polyester and wool.

Question 4.
Explain the properties of plastics.
Answer:
Plastics are those substances which are mostly synthetic in nature.
Following are the properties of plastics:

• Plastics are non-corrosive in nature, i.e., they do not react easily with air and water. They are unaffected by most of the chemicals in normal conditions.
• Plastics are the bad conductor of heat. They do not get heated up like metals.
• Plastics are non-biodegradable, i.e., they do not get decomposed by microorganisms.
• Plastics are very durable.

Question 5.
‘Plastics are hazard to environment’. Explain this statement.
Answer:
Yes, plastics are hazard to environment. They make versatile materials but are very dangerous to the environment. Plastics are non-biodegradable in nature. It takes more than 100 years to decompose. If use of plastics are not reduced, our earth would turn into a big garbage bin.
The major problems due to plastics are:

• If plastics are burnt, they evolve poisonous gases. These gases destroys the ozone layer of the earth and also pollute the environment.
• If the plastics are disposed in drains, they choke the drains causing waterlogging.
• If these plastics are swallowed by the innocent animals along with their food, they harm their di-gestive system which leads to their death.
• They are manufactured by the consumption of a large amount of petroleum.

Question 8.
List the strategies for plastic waste management.
Answer:
Some of the strategies for plastic waste management are:

• We should use paper bags and jute bags instead of using plastic bags.
• The government should ban the use of plastic bags.
• Plastics should be recycled to make other useful products which do not harm the environment.
• We should use a special garbage bins to dispose plastic wastes.
• We should not throw plastic wastes in water bodies.
• Practicing 4R’s principle, i.e., Reuse, Recycle, Reduce and Recover should be encouraged.